Reducing the exposure to oxygen of oxygen sensitive articles maintains and enhances the quality and shelf life of the article. For instance, reducing the oxygen exposure of oxygen sensitive food products in a packaging system maintains the quality of the food product and avoids food spoilage. Reduced oxygen exposure keeps the product in inventory longer, thereby reducing costs incurred from waste and having to restock.
One method of reducing oxygen exposure is to incorporate an oxygen scavenger into the packaging structure. Oxygen scavenging compositions are compositions that consume, deplete, or reduce the amount of oxygen in a given environment. There are a wide variety of different compositions that can be used in oxygen scavenging applications. Exemplary compositions are described in U.S. Pat. Nos. 5,211,875; 5,350,622; 5,399,289; and 5,811,027 to Speer et al. and WO 99/48963 to Cai et al., all incorporated by reference in their entirety. The oxygen scavenging composition can comprise a substituted or unsubstituted ethylenically unsaturated composition that is capable of scavenging oxygen upon activation or triggering. The oxygen scavenging composition can also include a metal catalyst and photoinitiators that help activate oxygen scavenging, and can be “triggered” by exposing the composition to a radiation source, such as actinic radiation, having sufficient power for a sufficient amount of time to initiate oxygen scavenging. High temperatures can also help trigger the oxygen scavenging composition.
Methods of triggering oxygen scavenging compositions typically use low-pressure mercury germicidal lamps that have an intensity output from about 5 to 10 mW/cm2. These lamps are commonly referred to as germicidal since the principal emission is at 254 nm. During UV light exposure, the compositions can also be heated to further enhance triggering. Heating the composition makes it possible to trigger the oxygen scavenging composition at a lower UV dose. Equipment systems and methods for triggering oxygen scavenging films and articles are disclosed in U.S. Pat. Nos. 6,287,481 to Luthra et al., 6,449,923 to Cook et al., 6,233,907 to Cook et al., and 5,911,910 to Becraft et al., as well as copending U.S. patent application Ser. No. 11/007,821 filed Dec. 8, 2004 directed to high speed triggering systems, all of these incorporated herein in their entirety.
In some circumstances, it may be desirable to limit or prevent an oxygen scavenging composition from further exposure or from being exposed to UV light. Current methods and equipment may rely on turning off the lamps to prevent or limit UV exposure. However, many germicidal lamps may be sensitive to being turned on and off. In some cases, increased on/off cycles may result in significantly shorter lamp life. Accordingly, there exists a need for limiting the amount of light to which an oxygen scavenging composition may be exposed that helps reduce the need to turn on and off the UV lamps.